Multianode electron tube and working circuit therefor



Aug. 28, 1945.

G. PASQUALIGO MULTIANODE ELECTRON TUBE AND WORKING CIRCUIT IHEREFOR Filed. June 5, 1942 Patented Aug. 28, 1945 MULTIANODE ELECTRON TUBE AND WORK- ING CIRCUIT THEREFOR Giulio Pasqualigo, Genoa, Italy; vested in the Alien Property Custodian Application June 5, 1942, Serial No. 445,888

' In Italy January 23, 1941 3 Claims.

This invention relates to multi-anode electron tubes in connection with suitable working circuits.

The basic principle of this invention is to replace the usual anode of the usual electronic tubes -(triodes, tetrodes, pentodes, etc.) by another more complex system of electrodes, which will be referred to hereinafter as recovering anode capable of recovering the kinetic energy developed by the impact of the electrons, which, in usual tubes has no useful effect on the working circuit and is lost as heat, especially when the tube is working in class A or B.

The recovering anode consists of a series of electrodes, the direct current potentials of which range from a given maximum positive value down to a lower value, which may be positive, nil or even negative. Said electrodes are connected together by means of condensers so that the alternating current component of the anode potentials is strictly the same for all electrodes. Things are to be so arranged that superposing in the system the said ranging direct current potential and the alternating current component of the anode tension (which last is the same as for a usual anode) there is always an electrode having an instantaneous potential very slightly positive with respect to the cathode, at least when space current is flowing. While the most positive of all electrodes has always the task of causing space current to flow and with just the same intensity as in a usual tube, electron trajectories are to be so arranged that electrons always impinge .on the electrode which in that moment is only slightly positive with respect to the cathode. Thus, while alternating current anode potential amplitude is limited by the direct current potential of the most positive electrode, which potential behaves as the direct current potential of a usual anode, anode dissipation is almost suppressed, because impact potential is reduced almost to zero.

The invention will'best be understood by reference to the following specification, taken in connection with the accompanying drawing in which:

Fig. 1 is a diagrammatic representation of a multi-anode tube and the circuits connected thereto in accordance with the invention,

Fig; 2 shows a modification of the invention illustrated in Fig. 1 and in which only two electrodes are employed,

Fig. 3 is a diagrammatic plan view of the arrangement of the electrodes of a tube such as is illustrated in Fig. 2, and

Fig. 4 is a view similar to Fig. 3 illustrating the arrangement of the electrodes when em-. ployed in a pentode tube.

Fig. 1 shows diagrammatically a multi-anode valve and electric circuit embodying the principle of the invention. l is the cathode; 2 the control grid; 33' are a pair of electrodes so arranged as to produce an electron beam; 4 are positive plates; 5 a plate maintained'at zero direct current potential; 6 are plates maintained at negative D. C. potential; I are other plates resonant anode circuit; 9 represents the load; In

is the inductance of the resonant circuit; II and I! are the terminals for the input signal; I3 is one of the electron trajectories; I4 is the symmetry axis thereof; l5 and I6 are feed batteries and I1 is the tube bulb.

The electron beam emerging from 3-3 and accelerated by the most positive ones of the electrode 4 (the most positive one may consist of a wire net portion fitted at right angles to the electron path so as to electrostatically act as a usual anode) follows a substantially parabolical path the form of which depends on the elctron velocity, i. e. on the instantaneous value of the alternating current anode potential component. By properly adjusting the distance between'the two electrode sets and the inclination oi the equipotential planes connecting each electrode pair 6-1 it is possible to cause at any moment the instantaneous trajectory to end on the proper electrode of the set. It is suilicient to arrange things so that the time taken by the electron to be longitudinally stopp d (to reach the top of the parabola) be the same taken thereby to be transverselly brought on to the set of capturing plates by the transversal component of the electric field set up between the two plate sets. The electron should be captured when near the top of its parabola. Secondary emission is avoided by the said transversal component present even on the surfaces of the capturing plates 4, 5, 6.

01 class B operation, the plates 6 become useless, v

because they have the right potential for catchstopped, then caught; then they are conveyed again, through the remaining part of the battery, to the same path (load-cathode) as with a usual tube, but "by avoiding the discharge of that part of the battery which would give the anode, in correspondence of the instantaneous value of the alternating current potential across the loads a surplus potential, which is quite useless for the economy of the circuit and which, once spent, should be somehow lost again.

The finer is the disposition of the anode potential along the anode sets, the better is the effect obtained. But even with tubes having only two anode electrodes the reduction of dissipation may be considerable.

Fig. 2 shows by way of example a tube with two electrodes inserted in a circuit for high frequency amplification, particularly adapted for use for modulated high frequency class B amplification.

i8 is the cathode, IS the control grid, 20 the most positive of the two anode electrodes having a window 48 which may be closed by a wire net; 2! is an antisecondary grid, 22 a less positive anode electrode, 23 a. condenser shunting the two anode electrodes as to high frequency; 24, 25 and 34 are high frequency chokes; 26 and 21 smoothing condensers; 28, 29 and 30 terminals for feeding direct-current tensions; 3! is a smoothing inductance; 2| a by-pass for the slightly positive bias battery 33 of the antisecondary grid 2!; 35 is the usual bias battery for grid i9; 36 a coupling condenser for the input signal; 31 and 38 the terminals for the input signal; 39 the neutralizing condenser; 40, M tank condensers; 42 a blocking condenser; 43 the inductance for the resonant circuit, 44 the coupling for the load.

The electron beam, controlled by the grid i9, shaped so as to be'slightly convergent, and accelerated by anode electrode 20, passes through window 45, then is decelerated and reaches anode electrode 22 if this one is positive; if not, it is reflected on anode electrode 20; it can be seen that in case of two electrodes the selection of the right electrode is obtained in a simpler Way.

In case of class B amplification of modulated high frequency, it is convenient to give electrode 22 half the direct current potential of electrode 20. Thus, when there is the carrier only, electrode 22 is always positive and is always the capturing electrode; this electrode, as an anode, works with full anode swing and has a practical efficiency of 66% instead of 33%, as would be, should the electrons reach directly either electrode 20 or a usual anode. When modulation intervenes, electrode 22 becomes negative for a part of the cycle and then electrode 20 is the capturing one; modulation can be increased up to a swing utilizing the whole direct current tension of electrode 20. Thus the output is just the same as with a triode having the anode direct current potential of electrode 20, but when only the caracsaeee rier is present, its efficiency is twice as much (the direct current anode current is delivered at half tension between the terminals 28, 39). When there is modulation, the emciency is always higher than in a usual tube, because electrode 22 is always working at least for one half of the modulation cycle.

Antisecondary grid 2! may be given a slightly positive bias, because otherwise electrons might be unduly, reflected even when electrode 22 is positive, due to the roughness of the equipotentlal surfaces near grid M.

It isto be remarked that the potential of electrode 22" has no effect on the value of the total anode current, because electrode 22 is screened value, power losses are low.

Fig. 3 shows a quasi-constructional arrangement of the electrodes of a tube having a two electrode anode. The same reference numerals indicate like parts as in Fig. 2. 45 are fins of electrode 20. The field between grid I9 and electrode 20 is convergent, so as to make the electron fiow into beams; fins 45 serve for heat dissipating purposes and for rendering the field external to electrode 20 divergent, in order to prevent the electron beam, once refiected, from nothing window 48 again, which fact would cause troubles in space charge and in the linearity of the characteristic, curves.

Fig. 4 shows a pentode with two anode electrodes. The parts existing in the tube shown in Fig. 3 are referred to by the same numerals: 46 is the screen grid and 41 the ordinary antisecondary grid of the pentode, which in this case is that having convegent properties, obtained by proper shape of said grid.

In the circuits in which the direct current anode current is fed through the resonant circuit inductance, it is possible to do without any high frequency choke even if a multiple anode tube of the above described types is used. In such case it is sufficlent that the various direct current tensions be brought to the various electrodes by leads contained in the main tubular lead of the inductance, from a zero high frequency point of said inductance up to an end of it. Known laws teach that the insulation among the various leads is loaded only by direct current potentials.

In the cases according to Figures 3 and 4, the outer electrode 22 may be part of the tube envelope so as to render it possible to cool same by means of a fluid like in ordinary cooled-anode tubes. The heat 0 f the inner anode 20 is generally dissipated by radiation, unless cooling by means of separate devices is adopted.

I claim:

1. A cathode ray tube of the character described, an anode construction comprising a plurality of individual plate members positioned in two spaced parallel planes with the plates in each plane forming a. set serially arranged, means connectin the first plate of one set with the second plate of the other set, further means connecting the successive plates of said one set to the successive plates of said other set, a control grid and a cathode in said tube adjacent said first plate, means forsupplying electrical potentials to the respective plates of said other set which potentials decrease in magnitude with increase in the distance between the respective plates and the cathode, and an output circuit connected between an intermediate plate of said other set and said cathode.

2. In an electron tube, a control grid, a cathode, an anode construction comprising a plurality of anode elements serially related with one anode element positioned nearer the cathode than the other anode elements and with the other anode elements positioned progressively further from said cathode, a plurality of individual direct current supply sources connected respectively between each anode element and the next anode element with the positive side of each supply source connected to the anode element nearer the cathode, and an output circuit connected between an intermediate one of said anode elements and said cathode.

3. In an electron tube, a control grid, a cathode, an anode construction comprising a plurality of anode elements serially related with one anode element positioned nearer the cathode than the other anode elements and with the other anode elements positioned progressively further from said cathode, means for supplying electrical potentials to the respective anode elements which decrease progressively in magnitude with increase in the distance between the respective anode elements and the cathode, and an output circuit connected between an intermediate one of said anode elements and said cathode.

GIULIO PASQUALIGO. 

